15.3% Efficiency All‐Small‐Molecule Organic Solar Cells Achieved by a Locally Asymmetric F, Cl Disubstitution Strategy

Abstract

Single junction binary all-small-molecule (ASM) organic solar cells (OSCs) with power conversion efficiency (PCE) beyond 14% are achieved by using non-fullerene acceptor Y6 as the electron acceptor, but still lag behind that of polymer OSCs. Herein, an asymmetric Y6-like acceptor, BTP-FCl-FCl, is designed and synthesized to match the recently reported high performance small molecule donor BTR-Cl, and a record efficiency of 15.3% for single-junction binary ASM OSCs is achieved. BTP-FCl-FCl features a F,Cl disubstitution on the same end group affording locally asymmetric structures, and so has a lower total dipole moment, larger average electronic static potential, and lower distribution disorder than those of the globally asymmetric isomer BTP-2F-2Cl, resulting in improved charge generation and extraction. In addition, BTP-FCl-FCl based active layer presents more favorable domain size and finer phase separation contributing to the faster charge extraction, longer charge carrier lifetime, and much lower recombination rate. Therefore, compared with BTP-2F-2Cl, BTP-FCl-FCl based devices provide better performance with FF enhanced from 71.41% to 75.36% and J sc increased from 22.35 to 24.58 mA cm −2 , leading to a higher PCE of 15.3%. The locally asymmetric F, Cl disubstitution on the same end group is a new strategy to achieve high performance ASM OSCs.

Simple thiazole-centered oligothiophene donor enables 15.4% efficiency all small molecule organic solar cells

“…A PCE of over 15% has already been realized by NFA based OSCs containing elaborately designed BDT donors. 25–30 Meanwhile, in spite of much lower synthetic cost, the development and PCEs of oligothiophene based donors have been unsatisfactory. From the era of fullerene acceptors to the present era inaugurated by NFAs, oligothiophene donors have been intensively investigated as electron-donating materials in organic photovoltaic research and technology.…”

“…All top BDT donors (PCE > 15%), without exception, are featured with the A–π–D–π–A backbone. 25–30 However, for high performance oligothiophene donors, it has been found that probably the A–π–A′–π–A structure is a more suitable design. Previously, by replacing the electron-donating central thienyl unit of DRCN7T with an electron-withdrawing di-chlorinated thienyl unit, SM donor 2Cl7T (Fig.…”

Effects of lateral-chain thiophene fluorination on morphology and charge transport of BDT-T based small molecule donors: A study with multiscale simulations

“…[13][14][15][16] Thus, all-small-molecule (ASM) OSCs based on both SM donors and non-fullerene SM acceptors may be promising candidates of new-generation high performance OSCs. 8,10,[17][18][19][20][21][22] To date, the highest PCE of binary ASM OSCs has reached 15.3%, 19,23 but it is still lower than the polymer-based OSCs (~18%). [1][2][3][4] Since the potential of the best non-fullerene FREAs has been proved in the high efficiency polymer-based OSCs, for ASM OSCs, its main task now is to improve available SM donor materials or find new promising SM donors.…”

Efficiency Improvement of All‐Small‐Molecule Organic Solar Cells Through Fused‐Aromatic‐Ring Side‐Chained Donors

“…[ 10–14 ] As a result, small‐molecule donors have high potentials for industrial application. However, the state‐of‐the‐art PCEs of single‐junction all‐small‐molecule (ASM) OSCs reach over 14%, [ 15–23 ] which are still lower than that of polymer‐based OSCs. The major challenge for further improving the PCEs of small molecule OSCs is to control the interpenetrating network of the donor/acceptor blends.…”